A guy named Roger Alsing whipped up a little program that encodes 2D images constructed of 50 semi-transparent polygons as artificial chromosomes. Each generation, candidate images were compared to a target image, the Mona Lisa, and those that were closer to the target were selected for reproduction.
He doesn't say what his algorithm or parameters are. Hopefully he'll share. Looks like he started with no polygons, and incrementally allowed them to mutate in, which is good evolutionary algorithm practice. Looks like it took just under a million generations to get something that's a pretty nice facsimile of the original.
Go check out the results.